1. Field of the Invention
The present invention relates generally to a magnetic disk apparatus and more particularly to a magnetic head unloading mechanism for use in a magnetic disk apparatus.
2. Description of the Related Art
There have recently been increasing demands for a magnetic disk apparatus of smaller size and with greater storage capacity as one of the computer external memories. One of the methods to realize greater capacity of the magnetic disk apparatus is to increase the number of magnetic disks put on the spindle and, in order to implement this method, the mounting distance of the magnetic disks in the magnetic disk apparatus is becoming smaller of late. Generally, a magnetic disk apparatus includes a rotatively driven spindle, a plurality of magnetic disks put on the spindle, a plurality of magnetic heads for writing data into the magnetic disk and reading data recorded on the magnetic disk, a plurality of spring arms each of which supports a magnetic head, a plurality of head arms each of which is joined at its end with each spring arm and fitted to an actuator shaft for rotation round the same, and an actuator for rotating the head arm.
In a magnetic disk apparatus for a computer, a floating magnetic head is being used to avoid damage from being caused by the contact between the head and the magnetic disk medium. By balance of the force for floating the head due to air flow generated by the magnetic disk rotating at a high speed (for example, 3600 rpm) and the force of the spring arm pressing the head against the disk, the magnetic head is floated above the magnetic disk with a fine gap (approximately 0.15 .mu.m) held therebetween and in such a state performs read/write of data on the magnetic disk. When the rotation of the magnetic disk is stopped, the magnetic head comes to contact the magnetic disk urged by the spring force of the spring arm. Since the surfaces of the magnetic disk and the magnetic head are both finished in mirror surface, the magnetic head tightly adheres to the magnetic disk. Therefore, when the magnetic disk is rotated at the time of restarting the apparatus, overload is placed on the spindle motor and, if then it is attempted to rotate the disk by force, there are dangers of breakage of the magnetic head and/or damage on the surface of the magnetic disk. Especially when a small and low-torque spindle motor is used in the latest magnetic disk apparatus which is smaller in size and designed for greater energy saving, it poses a serious problem to restart the apparatus when the magnetic head has adhered to the magnetic disk.
In order to solve the above mentioned problems, there is known a magnetic head unloading mechanism, in which, at the time when the apparatus is stopped, the magnetic head is separated by force from the magnetic disk. Referring to FIG. 1, an example of conventional magnetic head unloading mechanism will be described below. In the vicinity of the magnetic disk 1 rotated at a high speed (for example, 3600 rpm), there is disposed an actuator assembly 2 adapted to swing so as to cross the tracks of the magnetic disk 1. At the distal end of a spring arm 3 of the actuator assembly 2, there is provided a magnetic head 4 performing read/write of data on the magnetic disk 1. In the vicinity of the magnetic disk 1 and within the turning radius of the actuator assembly 2, there is disposed a bar 5 with a slant face 5a formed at its distal end with which the spring arm 3 can make slide contact. The portion of the slant face 5a of the bar 5 is arranged in a taper form becoming gradually narrowed toward the tip.
When the disk 1 is rotated on high speed the magnetic head 4 is slightly floated above the magnetic disk 1. As the actuator assembly 2 swings, the magnetic head 4 is moved to a position over the target track of the magnetic disk i and performs read/write of data on the magnetic disk 1. When the apparatus is stopped, the actuator assembly 2 is swung in the direction of the bar 5 so that the spring arm 3 goes on the slant face 5a of the bar 5. Thus, the end portion of the actuator assembly 2 is supported by the bar 5 with the magnetic head 4 separated from the magnetic disk 1. When the apparatus is restarted, the magnetic disk 1 is rotated on high speed again and the actuator assembly 2 is swung in the direction of the magnetic disk 1 and, thereupon, the magnetic head 4 performs read/write of data on the magnetic disk 1.
With the conventional head unloading mechanism as described above, a large turning angle of the actuator assembly 2 is required for unloading the magnetic head 4 with the bar 5. Hence, there arises a problem that a large space becomes necessary and it hinders the magnetic disk apparatus from being made smaller in size.
Referring to FIG. 2, another example of conventional head unloading mechanism will be described below. In this example, a solenoid 6 is disposed in the vicinity of the magnetic disk 1 and a plunger 7 is adapted to be driven by the solenoid 6. The end of the plunger 7 is formed to become gradually narrowed toward its tip and have a slant face 7a thereon, with which the spring arm 3 of the actuator assembly 2 can make slide contact.
When the magnetic disk 1 is rotated on high speed, the magnetic head 4 slightly floats above the magnetic disk 1. The actuator assembly 2 swings so that the magnetic head 4 is moved to a position over a desired track of the magnetic disk 1 and, thereupon, the magnetic head 4 performs read/write of data on the magnetic disk 1. When the apparatus is stopped, the actuator assembly 2 is swung in the direction of the solenoid 6. The solenoid 6 drives the plunger 7 in the direction of the magnetic disk 1 so that the spring arm 3 goes on the slant face 7a of the plunger 7 and, thus, the distal end portion of the actuator assembly 2 becomes supported on the plunger 7 with the magnetic head 4 separated from the magnetic disk 1. When the apparatus is restatted, the magnetic disk 1 is rotatively driven on high speed again and the actuator assembly 2 is swung in the direction of the magnetic disk 1 and, thereupon, the magnetic head 4 performs read/write of data on the magnetic disk 1.
According to this example of conventional design, the turning angle of the actuator assembly 2 can be made smaller than that in the example of conventional desion shown in FIG. 1 because the plunger 7 driven by the solenoid 6 moves toward the actuator assembly 2 to receive it at the time of the head unloading. However, in the present example, mechanism and power for driving the solenoid 6 come to be required.